JP2006311686A - Reactive power compensation device for generator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a reactive power compensation device for a generator that connects a power capacitor of a proper amount to a power supply and releases it thererfrom at the same potential according to an amount of reactive power generated by an induction motor, and reduces power consumption by controlling a power factor of the induction motor in the range of 1 to an arbitrary value. <P>SOLUTION: The reactive power compensation device for the generator is characterized by measuring the reactive power that the induction motor consumes, operating the necessary capacity of the power capacitor 12, and controlling the power factor of the induction motor in the range of 1 to the arbitrary value. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a reactive power compensator for a generator that can reduce a starting power when an induction motor is operated using a generator power source.

  In general, when an induction motor is operated, a very large current of 7 to 10 times the rating flows at the start.

  In order to suppress this starting current, a star delta start, a reactor start, and the like are generally used, but in this case as well, an induction motor is operated with a current of about 3 to 5 times the rating.

  A starting power graph of the induction motor is shown in FIG.

  As can be seen from this graph, when the induction motor is started, a very large reactive power is generated, and it can be inferred that the element that increases the starting current is due to the generation of the reactive power.

  Thus, when selecting the power supply capacity necessary to operate the induction motor with the generator power supply, it is necessary to select a generator that can supply the apparent power including the large reactive power generated when starting the induction motor. is there. In general, a generator with a capacity three times that of the output (horsepower) of the motor is selected.

By the way, there is known an electric motor that compensates reactive power with a phase advance capacitor in consideration of power factor control, power factor improvement, starting method, and starting power (for example, see Patent Documents 1, 2, 3, and 4). .).
JP 09-215360 A Japanese Patent Application Laid-Open No. 07-107671 JP 2001-145265 A JP 2000-224767 A

  However, according to the above technology, the phase advance capacitor connected to cancel the reactive power of the induction motor is used for the purpose of improving the reactive power during operation. Connect to. At this time, when the induction motor is stopped, the current advances to the phase advance capacitor, and reactive power is generated. Again, due to the nature of the capacitor, secondary generation such as generation of harmonics due to resonance with the power supply system and increase of the power supply voltage. May cause serious power failure. Further, since the reactive power generated by the induction motor varies depending on the load factor of the induction motor and the slipping state, there is a limit to improving the reactive power generated from the induction motor with only a fixed capacitor.

  Further, when connecting the phase advance capacitor to the power supply, if the instantaneous voltage of the power supply and the terminal voltage of the phase advance capacitor are not at the same potential, an open / close surge voltage may be generated, causing noise disturbance and the like.

  In order to cancel the reactive power generated by the induction motor, it is possible to connect a power phase advance capacitor to the power source, but it is necessary to select a capacitor capacity equal to the amount of reactive power generated by the induction motor.

  When an induction motor is operated with a generator power supply, the reactive power generated at the start-up is offset to reduce the reactive power current and make the apparent power required for starting almost the same as the active power. If this is possible, the generator capacity can be reduced as a result.

  Therefore, according to the present invention, an appropriate amount of a phase advance capacitor is connected and released at the same potential according to the amount of reactive power generated by the induction motor, and the power factor of the induction motor is controlled to 1 to an arbitrary value. It is an object to provide a reactive power compensator for a generator that reduces power consumption.

  The power factor is a ratio of active power / apparent power, which is a rough indication that the reactive power is small if it is close to 1, and the apparent power is the sum of the reactive power and the active power.

  In order to solve the above-described problems, the present invention has a configuration as shown in the following (1) to (3).

  (1) Reactive power compensation for a generator characterized in that the reactive power consumed by the induction motor is measured, the required phase advance capacitor capacity is calculated, and the power factor of the induction motor is controlled to 1 to an arbitrary value. apparatus.

  (2) For the generator according to (1), the timing of connection of the phase advance capacitor is controlled by firing the thyristor when the instantaneous voltage of the power supply and the capacitor terminal voltage are at the same potential, thereby suppressing the generation of the surge voltage. Reactive power compensator.

  (3) Capacitor capacity equivalent to the generated reactive power can be selected, and the capacity of capacitors can be divided into 10, 20, 40, and 80 capacity, and fine capacitor capacity can be selected by combining necessary capacitors. The reactive power compensator for a generator according to (1), characterized in that:

  According to the present invention, the starting power factor of the induction motor and the reactive power generated during operation are improved by the generator reactive power compensator, and the power supply capacity can be reduced.

  Induction motors are used in machines such as rotating machines. Especially when a generator power source is used as a power source for a construction site, the capacity of the generator can be reduced, and the fuel and cost of use can be reduced. Reduction is possible.

  In addition, it can be expected to reduce greenhouse gases by reducing the amount of fuel used.

  One embodiment of the present invention is shown in FIG.

  This is a connection type in which a reactive power compensator for a generator is inserted between the generator power source and the induction motor.

  In the drawings, 1 is a generator power source, 2 is a power connection terminal, a terminal for connecting the output of the generator, and 3 is a load connection terminal for connecting a load such as an electric motor. 4 is an analog-digital converter, a circuit for converting an electric signal, and 5 is a control device, which calculates active power and reactive power, calculates an appropriate capacitor capacity, and generates a thyristor control signal, 6 Is a rotating device incorporating an induction motor, a load device that generates reactive power, and 7 is a current transformer that constitutes a current detector. A transformer 8 constitutes a voltage detector. Reference numeral 9 denotes a capacitor unit. Capacitor units with large capacities such as 10, 20, 40, and 80 are arranged in stages, and fine capacitors can be connected to the power source. Reference numeral 10 denotes a circuit breaker, which operates in the event of a failure and serves to disconnect the abnormal circuit from the generator power supply. A thyristor 11 is turned on / off by a control signal from a semiconductor switch control device used to connect the capacitor to the generator power supply 1 at high speed. A phase advance capacitor 12 is used to cancel reactive power generated by the motor. A power calculator 13 calculates voltage, current, active power, apparent power, reactive power, power factor, frequency, and the like. Reference numeral 14 denotes a closing command calculator, which calculates a capacitor capacity necessary for canceling reactive power and distributes necessary capacitor units. A pulse distributor 15 has a function of starting a thyristor arranged in the capacitor unit when the power supply voltage and the capacitor terminal voltage are at the same potential.

  Next, the operation flow of the present invention will be described.

  When the rotating device 6 is started and operated, power including reactive power is consumed. At this time, a large amount of electric power including reactive power as shown in FIG.

  From the detectors 7 and 8, the power calculator 13 calculates the current voltage, current, frequency, active power, reactive power, apparent power, power factor, etc. from the power supply voltage and current through the A / D converter 4. For the reactive power calculated by the power calculator 13, a capacitor capacity necessary for canceling the reactive power is calculated by the input command calculator 14, and the capacitor unit 9 is selected. The capacitor unit 9 selected by the input command calculator 14 is on / off controlled by the pulse distributor 15.

  The reactive power generated from the rotating device 6 is canceled by the power phase advance capacitor 12, and the reactive power is reduced at the point of the power connection terminal 2 as shown in FIG. Become.

  According to this embodiment, the reactive power generated by the induction motor is improved in power consumption by the generator reactive power compensator A, and the power consumption applied to the generator power source 1 is reduced.

It is a connection diagram which shows one Embodiment of this invention. It is the graph which showed the electric power which an induction motor consumes. It is a graph which shows the power consumption at the time of using the reactive power compensator for generators.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Generator power supply 4 Analog-digital converter 5 Control apparatus 6 Induction motor built-in rotary device 9 Capacitor unit 11 Thyristor 12 Phase advance capacitor for electric power

Claims (3)

  A reactive power compensator for a generator, which measures reactive power consumed by an induction motor, calculates a necessary phase advance capacitor capacity, and controls the power factor of the induction motor to 1 to an arbitrary value.   2. The reactive power compensator for a generator according to claim 1, wherein the thyristor is ignited when the instantaneous voltage of the power supply and the capacitor terminal voltage are at the same potential to suppress the generation of the surge voltage. .   In order to select a capacitor capacity equivalent to the generated reactive power, the capacitor capacity is divided into 10, 20, 40, 80 every certain capacity, and the required capacitor can be combined to select a fine capacitor capacity. The reactive power compensator for a generator according to claim 1, characterized in that:

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